Impregnating wood and the like



' Feb. 19, 1935. F, H, LYONS 1,991,811

IMPREGNATING WOOD ANQ THE LIKE Filed Feb. 17, 1932 2 Sheets-Sheet l Feb.. 19, 1935. F. 1-1. LYONS IMPREGNATING WOOD AND THE LIKE 2 Sheets-Sheet 2 Filed Feb. 17, 1932 Patented Feb. 19, 1935 UNITED STATES PATENT OFFICE IMPREGNATING WOOD AND THE LIKE Frank H. Lyons, Memphis, Tenn., assignor to I E. L. Bruce Company, Memphis, Tenn, a corp'oration of Delaware Application February 17, .1932, Serial No. 593,694"

3 Claims.

the wood without injuring its structure.

- A further object is to thus heat the wood preliminary to subjecting it to an impregnating composition to preserve it against attacks by fungi and termites.

One way heretoforegn which to impregnate the wood has been found-"to be by the open tank method, in which-there are two separate tanks containing the treating composition, one at a higher temperature than the other. In such a method, the wood is heated in the first tank, by immersion in the composition, to expand the air in the-.cells of the wood and is then immersed in the second tank, which is at a lower temperature. As the air in the cells of the wood contracts on cooling, by immersion in the second tank, the composition is sucked into the cells and thus the wood becomes impregnated.

In order to avoid injuring the wood in the heating operation in thisprocess, care must be taken,- otherwise the wood may case-harden and check.

One of the objects of this invention is to suitably heat the wood, before immersing it in the impregnating composition, without injuring its structure, and so that the pores of the wood, large and small, shall be open at the time the wood products are ready for immersion in the composition.

Lumber to be treated may vary in its moisture content from about 425%. Lumber with the higher moisture content is used for rough construction work, such as joists, subfiooring, etc., while lumber with a lower moisture content, around about 8%, is used for flooring, sash, doors, frames and general trim work.

In order to properly impregnate lumber with such a varied moisture content without changingthe physical characteristics of the wood, means must be provided by which this can be done without affecting the moisture content of the wood.

One of the objects of the invention is to heat the lumber to the desired temperature in an atmosphere of such relative humidity as that there will be a proper balance with the moisture in the wood. In other words, in heating wood with a certain moisture content, an atmosphere of proper relative humidity is maintained, so that the wood, during the heating process, will not absorb nor lose moisture.

For carrying out my process,'various arrangements of apparatus may be employed but that herein shown and described has been found to be satisfactory in operation.

Referring to the drawings: Fig. 1 is a sectional plan view,

Fig. 2 is a vertical section on the line 2-2 of Fig. 1, 4

.Fig. 3 is an enlarged section on the line 3-3 of Fig. 2,

Fig. 4 is a section on-the line 4-4 of Fig. 3,

Fig. 5 is a section on the line 5-5 of Fig. 4, and

Fig. 6 is a detail view showing the cross bar for the lumber'carriage.

The lumber is first heated in the chamber 10 and is thereafter immersed in the tank 11 that contains the treating composition, which is at a lower temperature. For handling the lumber, a line of track 12 is provided on which runs the carriage 13. In the bottom of the heating-chamber 10 is" a steam radiator 14 made up of a series of pipes connected with a heatsource 15. For injecting steam into the heating chamber there is a pipe 16, that has apertures 17, that sprays the steam in horizontally and a pipe 18, that has apertures 19, that sprays the steam vertically, the said pipes being connected with a source of steam through the cross pipe 20 and inlet pipe 21. Mechanical means for circulating the air and steam may or may not be used. Doors 22 are for-closing the heating chamber.

The treating tank may have removable bulk-- heads 23 for changing its size to suit various lengths of stock. A pipe 24 leads into the bottom of the tank for supplying the treating solution thereto. Pumps or agitators may be used for circulating the preservative in the tank.

Any suitable truck 25 for supporting, the lumber may be employed. .The truck consists of a cross bar 26 having brackets 2'7 in which are mounted wheels 28, and brackets 29, through which pass pins 30, to which are swiveled, side bars 31. In the side bars are holes 32 for adjusting the cross bars that support the load. The two trucks are connected by a spacing rod 33 passing through a hole in thereceiver 34. A top and lock cross bar 35 has lugs 36 that enter holes 32 in the side bars and locking pins 37 hold the parts in assembled relationship. A lifting eye 38 is carried by the cross bar that engages with a lifting bar. crane, a monorail 39 is supported from the top of the building.

- In operation, the wood is suitably stacked on' the carriage and is rolled into the heating chamber after the desired temperature and humidity For supporting a lifting properly balanced with the moisture content of the wood products exist in the chamber. This same temperature and same humidity are maintained for a period sufiicient to heat the lumber. At the end of that period, the carriage and lumber are rolled out, the lumber is removed from the carriage by the overhead crane running on the rail 39 and is immersed in the treating solution in the tank 11, for a period until the wood has absorbed the desired amount of treating solution.

Automatic temperature and humidity control is provided for convenient operation of the heating chamber. The proper operation and control of the heating chamber is of importance in producing uniformly preserved lumber.

The following wet and dry bulb temperatures for heating chamber humidity, have been determined to be satisfactory in heating sash, frames, lumber, etc., with a given moisture content without injury to the stock:

It is apparent, of course, that for the temperature, humidity and time periods indicated, there will be a substantial sterilization of the wood,

which is desirable before the preservative treatment. t

The following treating schedules for difierent structural and finished types of wood have been found satisfactory;

Length of Length of time time heated dipped Sash Pondosa pine )4 hour. be hour. Frames Pondosa pine 54 hour)... V -$4 hour. 1'' lumber southern yellow pine 1 hour 1 hour. 2 lumber southern yellow pine 1% hours 1 hour. 3" lumber and up southern yellow pine 2 hours 1 hour.

The dry bulb temperature should not be over 190 F. while the stock is in the heating chamber. The wet bulb temperature should always indicate moisture conditions such as will not unbalance the moisturecontent of the stock. The heated lumber should be lowered into the treating solution without delay after removal from the heating chamber, otherwise absorption and ,penetration will be reduced. The temperature of the preservative, should not exceed 90 F. The treating composition may be pumped through a cooler to insure the proper temperature.

It may be desirable to shut off the steam that is used to maintain the humidity, about ten or fifteen minutes before the lumber is removed from the heating chamber and to exhaust the very moist air, so that when the chamber is opened, there will be no condensation of moisture on the wood due to contact with the cool air, as the lumber is brought out ready to go into the treating tank. This insures that no water will condense on the surface of the wood and raise the grain of the wood. It is desirable too, to keep water out of the treating composition as far as possible.

From the above description it will be clear that the lumber is first heated to approximately 190 F. so that the air in the cells will be expanded and a high absorption and penetration of the treating composition will be obtained, when the hot lumber is immersed in the colder treating composition, due to the resulting contraction of the air. When the proper degree of humidity is maintained in the heating chamber, the cells of the wood open up or remain open, so that the wood will absorb the treating composition in the proper amounts. If the humidity of the heating chamber is maintained so that there is no loss of moisture or drying out of the wood nor any undesirable increase in the moisture content of the wood, then the desired penetration of the wood can be had without otherwise substantially changing its physical characteristics.

The heating chamber is operated under controlled conditions so that its atmosphere has a relative humidity that is in equilibrium with the moisture content of the wood to be preserved so that no ingress or egress of moisture from the wood occurs.

While I have described my invention in connection with the impregnation of wood with a preservative, it will be clear that other materials than wood could be similarly impregnated with various types of compositions.

I claim: 1. A method of impregnating wood containing moisture comprising heating the wood in an atmosphere having a relative humidity that will not substantially change the moisture content of the wood, and then treating the wocdwith a non-aqueous solution of lower temperature.

2. A method of impregnating wood containing from about 23-25% moisture comprising heating the wood to about 190 F: dry bulb temperature in an atmosphere having a relative humidity that will not substantially change the moisture content of the wood, and then treating the wood with a non-aqueous solution of lower temperature.

3. A method of impregnating wood containing moisture comprising heating the wood in an atmosphere having a relative humidity that will not substantially change the moisture content of the wood, decreasing the relative humidity before the end of the heating period to inhibit the precipitation of moisture on the surface of the wood as.it comes in contact with the cold air and then immersing the wood in a non-aqueous impregnating solution.

FRANK H, LYONS. 

